Furnace for burning comminuted fuel, including tangential air feed



Aug-15, 1950 6.1'. LESTER, sR 2,518,800

- FURNACE FOR BURNING COMMINUTED FUEL,

INCLDING 'I'IKSENTIAI..` AIR FEED A 3 Sheets-511661 l Filed July 14, 1948 (laca/:smaad Carbon Parz'cZea lllllfln 650265 7.' es rE/z, .s/z.

Aug. 15, 195o G. T.' LESTER, sR 2,518,800 'FURNACE FOR BURNING COMMINUTED FUEL, INCLUDING TANGENTIAL AIR FEED 3 Sheets-Sheet -2 Filed July 14, 194s FUEL HOPPER 26 FUFL & A0?

G50/20er far-ER, .s/z.

Aug. 15,V 1950 G. T. LESTER, sR

FURNACE FOR BURNING COMMINUTED FUEL, INCLUDING TANGENTIAL AIR FEED 5 Sheets-Sheet 3 Filed July 14, 194s MUNI \\\\\\\\\\\\ l1|||| ||llllllllllllllllllllllllll ,GITYs GEORGE 7.' LES TAE/2,67?.

Patented Aug. l5, 1950 UNITED-*STATES PATENT: OFFICE FUR-NACE Fonv BURNING fCoMMINUTED FUEL, riNCLUDiNe. TANGENTIAL `AIR George T. Lester, Sr., Martinsville, Va. `Aplllicxtlioll Jllly 14, 1948, Serial N0. 38,634

1 This invention relates to'a furnace for efficiently producing smokeless combustionof comminut# ed fuel. L ,.jn y One of the objects of the invention is to provide a` means forgenerating heat from comminuted fuel such as sawdust, pulverized coal, etc., by burning the fuel infa combustion chamberA in a 'whirling `atmosphere continuously supplied, causing" the products of combustionto expand into a chamber more capacious than-the com` bustionchamber and -of larger diameter, the combustion products still whirling with suiiicient velocity to throw unconsumed particles lto the periphery of the expansion chamber, thereby creating a clarified central column of combustion gases which flows to the heat exchanger, usually a boiler, and ultimately to the stack, and creating adownward drift of the atmosphere of the expansion chamber adjacent the peripherythere-r of and its return to the combustion chamber with the'fcentrifu'gally displaced unconsumed fuel particles, sothat'the combustion of said particles can be completed.- A Another object of the invention is toprovide, in a furnace of the typefwhich has a combustion chamber and a vsuperposed expansion chamber of `greaterc a'macity and-diameterl than the come bustion chamber, with a restrictedfmouth begtween'said chambers, in which fuelis'burned in said combustion chamber in a whirlingr atmosphere `produced by the admission ofair'under pressure in a circumferential direction, -andfin which the `whirling products of combustion expand within the expansion chamber, whereby unconsumed particles are thrownto the periphery,7 of said chamber; but by virtue of the expansion are' under less 'pressure'tha'n that in the combustion chamber, passages-communicating with the peripheral portion of said expansion chamber and with said-'combustion chamberrand means fordrawing the centrifugally displaced unconsumed particles through said passages' into said combustion chamber against the superior pressure existing in said combustion chamber.

A further object of the invention is to provide a furnace of the type described, having a refractory lining in the combustion chamber inter sected by circumferential-series of air inlet tubes .in zones adjacent the bottom, top, and intermediately, whereby the lining is `sufficiently cooled to prevent it from fusing, andthe entering air correspondingly preheated.

Other objects of the invention will Vappear as the following description of a preferred and vpractical embodiment thereof proceeds. t

. coiaims. (miic- 28)v In theV drawings which accompany and form a part of the specification:

Figure l is a vertical section through a furnace and the associated end of a vertical boiler, em

bodying the principles of the invention, taken along the line l-I of Figure 3, viewed in the direction of the inner arrows;

y Figure 2 is a similar View of the furnace on the same section line, viewed in the direction of the outer arrows; i

Figure 3 is a cross-section taken along the line 3 3 of Figure 1;

Figure 4 is a fragmentary detail in vertical section of a portion of therefractory lining of the combustion chamber, showing an upper and lower tuyre; i

Figure 5 is a fragmentary detail in vertical section through a portion of the refractory lining showing one of the injectors;

Figure 6 is a cross-section taken along the line 66 of Figure 5;

Figure 7 is a horizontal section through thc door opening showing the door and adjacent environment, taken along the line l'-1 of Fig ure 2; f v i Figure 8 is a Vertical section taken along the line B-B'of Figure 7.

i Referring now in detail `to the Vdescription of the invention as illustrated, the numeral l represents av cylindrical furnace upon which a tubular boiler 2 is mounted coaxially of the furnace.' 'The crown sheet 3 4of the boiler is some distance within the boiler shell .4, the space 5 within the shell and below the crown sheet being hereinafter referred to as the expansion chamber.

The furnace comprises a metal casing 6, provided on theinside both on the bottom and sides, with a refractory "lining 1, whichA lining defines a combustion. chamber 3, the bottom of Vwhich preferably has a slightly concave depression in the middle, as indicated at 9,*and the sides of' which converge upwardly, forming a somewhat retricted mouth lll, communicating with the eX- pansion chamber, and also defining an annular mantel H, surrounding the mouth and forming the bottom ofthe expansion chamber. The casing 6 is provided with an air jacket l2. surrounding the combustion chamber, supplied with air under some pressure by a blower I3, controlled by a valve 26. A pressure of one-half pound may be mentioned as a practical working pressure, but this may be varied, within the invention, according to the conditions of use. The jacket 'I2 is the reservoir for all the air supplied' to the combustion chamber, including that which comes in as a vehicle for the fuel. The jacket i2 is preferably coextensive with the height of the furnace, in View of its cooling effect upon the sides of the refractory lining '1.

A circumferential series of uniformly spaced tuyres Ill open into the combustion chamber in a Zone adjacent the bottom. These communicate with the jacket. l2; extend. radially throughy the refractory lining, terminate as close as possible to the inner surface of said lining, and are closed at their inner ends except for a single'4 lateral hole l5. The holes ofv all the. tu-yres IIL face in the same circumferential direction, serving as nozzles to organize a whirling atmosphere within the combustion chamber.

Another circumferential series of tuyres- H'V open into the combustion chamberv infthe. zone of the mouth IB, communicating with the jacket l2, passing through the refractory lining7 in an upwardly inclined position, and terminating in the relatively thin. lip of 'refractory'material that bounds the circumference ofz't-heimouth; Thesey tuyres likewisev are-closest;at-'therr ends, except for the single. lateralesholes; t] whiclr face in the same. direction; as. the holes.' iir the lower: series of tuyres. The. function of the.- tuyresi I6is. to augment the whirlingl movement of' the gaseous atmosphere of the combustion chamber, as well as to, provide additional air for combustion. They also cool the upper part of the refractory lining through which they:-extend,` and give. it structural support.

The casing 6 is provided with arectangular metal frame.- l 8:; at a pointzntermerliate'its height, dening a door opening.I which: gives; access to the interior of the combustion chamberfor kindling a fire, andi also serving-s as a manhole. The framev i8 bridges: the jacket space,- being welded or otherwise secured to. then-inner' and outer jacket walls. in an; airtight manner; all around. The sides and bottom members of the frame I8. terminate flush with the inner and outer jacket' walls,-bu.t` the; top member 1'9 projects inwardly` for a distance equal to the thickness of the refractory lining so as to support the overlying refractorjtmaterial. The topfframe member I9 is hollow and has holes'.y 20- therethrough, which communicate with the; air'jacket l2, and the drawings: show that two; 'of the tuyres of the upper series, ttc-are weldedy to the member I9, cozmnunicatingwith. said vjacket through the interior ofk saidm'ember.. Air passing through said tuyres; from the, jacket I.2 cools the member' I9. asuwell as the refractory material through which: theY` tuyres: |611 extend. The refractory,l liningV 'l5' hasV an* opening therethrough substantially congruent: with the door opening dened by the frame li8.:

A door 2l is hinged' tothe outer walt of theair jacket atV theapproach sideV of: the door opening,

. with respect to the directiorrof' circumferential travel of the gases. within the'combustionchamber, and closes against said outer wall. Said door carries an'. inclined'. baiiie 2-2; spaced therefrom andfsupported by. rods 232 'Saidbaile starts substantially Iiush withfdthe inner-wall of the jacket I2, at the hingedside of the"cloor:, and terminates substantially flush withA the inner surface of the refractory lining; atthe opposite side. The main-1 objectzof the baffle is tostreamline the whirling gases passi'ngrthel door; opening', so that they, will not; strike' abruptl-y'the; refractory lining adijacent the freeside ofithedoon and create turbulence.V which would. interrupt the orderlyv undidirectlcnali` circurrrferentialll swirl. of

said gases. Its other object is to protect the door from becoming unduly heated. The aggregate cross-sectional area of the rods 23 is the minimum required for their necessary supporting strength, and presents the minimum thermally conductive path from baffle to door.

Comminuted fuel is supplied gravitationally through-a pipe; 242, which passes. through the casing Biand the refractorylini-ng 1, intersecting the air jacket l2. The inner end of this pipe opens into the combustion chamber adjacent the appreach, side off the door opening and is inclined toward the baille.. at such an angle that the resultant of gravity and the circumferential swirl of the gaseous atmosphere of the combustion chamber-causes the entering fuel to spiral downwardly .tow-ard; the concave middle of the refractory bottom A pipe 25 taps the jacket I-2f` and; enters the fuel pipe 24 at some distance from the furnace, the gravitational ow of fuel toward the 'combustion chamber being.;- assisted bj'air at; jacketpressure. The fldvvr of this' air past the baffle cools the bafie.

In starting'aaU coldaffurnacer,theI lirey can be mos-t; conveniently; kindledr. assumingv that. the fuel, iss'sawdust; by' throwing; apiece of lighted oil-soaked 'waste through thedoor' opening onto the floor of the combustion chamber near the middle; The: air-valve l2t.f-is;then.openedi to admit air to the jacket. l-2-;. thus organizingY- the whirling atmosphere-Withinthee combustion chamber. The fuel isrthen, admi.ttedwhich@ deposits upon the burningywasteand is. ignited. At first, a mass. of fuel. may. accumulate the depression 9,. burningv from they topi; butsasv the heat intensiies, most .off the.t fuel-tis.:A burned-in suspension beforeI it reaches-the bottom of theffurnace, any pile that. may; have previouslyl accumulated` beingl progressively burned away by4 attrition. When. the furnace: isfinffullcombustion, the.l combustion chamber isulledi with whirling flame sov intense that,v the surfacer of. the' refractory lining is heated to white:incandescence,l atwhich temperature the." bestt knownlining material would. melt if; it were: notion the distributed coolingv ofv thefsame'1 effected: by the .proximity of theair jacket.:` I 2;,the. airfpassingq-y through the lower andL upper s ,eri'es of tuyres i4 and l5, .tha air admittedL withf fuel; and yair flowingV throught-'passages in; an.: intermediate zone of` said. refractory; lining, presently to` be' described.

Theiiaming, products ofy combustion issue from the mouth tfunder -thefcom-bnecl forcesr of 'convection, thermal.l expansion and; displacement by theair entering; theecombustion-chamber, and they riser in'.A the fern-ref` arwhirlingcolumn which expandsinthe expansion: chamber,y 5, thel` latter being of greatercubic capacity?than the com-bustion. chamber; AInfapraatica-1 embodiment of the invention fnoiv--infsuccessful' operation; the Aexpansion chanlberfr has eight times' tha-volume of. the combustionchamben.; Expansionreduces the upwardfvelocitycfzthe ascending-,- column .oi combustionfpro ducts givingftimerforthe substantial completion' of combustifm in= the; expansion chamber so. that` thef 'amesi. dier out: before reaching the crown: sheet, the-flatterfbeing-thus protected from excessive :heating with l tha attendant=risk; of producingjasteam pocket attheiadjacent end-.of the boiler;- forcing-5f thefwater back and` leavingdry boiler surface to be'overheatedfbythefintensely hot' amesi opemendaof'the-fboil'er tubes 3 in tha-crown sheet 3 are;P as;v is;- 'eustcmary, uniformly distributed: throughout Ltrei area; of the crown sheet,res,ulting in a uniform discharge of the combustion products of the furnace throughout thearea ofthe crown sheet, produc--v ing the symmetrical vortex indicatedby the arrows inlFigure- 1. e

The combustion products in the expansion chamber are, however, interspersed with a constituent of incompletely consumed fuel particles which ordinarily would be drawn through the boiler tubes and appear at the top of the stack as smoke, representing wasted fuel, besides, fouling the boiler tubes and depositing a heat insulating carbon` filmV on the interior surfaces of the tubes, thus decreasing the efficiency of the boiler. These unconsumed particles are centrifugally thrown toward the periphery of the expan-1 sion chamber, clarifying the central column of gases vrising throughsaid chamber. The heavier particles, strike the inner surface of the shell 4 and, their motion being arrested, they-drop upon the mantel Il. rihe lighter particles circulate suspended in a peripheral zone of combustion gases `outside of the central clarified column. The diminution inthe velocity of ascent of the com-V bustion products in the expansion chamber gives time for the complete centrifugal separation of the unconsumed fuel particles before the comb ustion gases enter the boiler.

The `present invention'provides for the return of these unconsumed particles to the combustion-chamber to be burned, and the problem is tok withdraw them from a region of relatively less pressure and to introduce them into a region of relatively greater pressure. This is done in the following manner.

A series of injectors 2l is provided, embedded in therefractory lining l in alternate arrangement with respect to most of the tuyres i6. Each injector, as shown, consists of a vertically positioned carbon tube 2S, having its upper end opening in the face of the mantel Il near its outer periphery at the ,bottom of a funnel shaped depression 28a, formed. in said mantel. Said carbon tube is surrounded by a'larger tube 29, forming an annular air conduit thereabout. At thefside of theannular air conduit and axially parallel thereto is an air pipe 3i), communicating with sai-dyannular conduit near the top and com-` municating at its lower `end with the air jacket l2. rI'he vlower ends of the carbon tube 23 and the surrounding tube 29, in the same zone, are inwardly beveled toform yinner and outer nozzles 3i andV 32. Air entering the pipe 3% under pressure from theairjacket l2 issues from the nozzle 32, creating suction at the nozzle 3i. This induces a `down driftof the atmosphere of the eX- pansionchamber in the peripheral region, drawing4 it back into the combustion chamber together with thedisplaced unconsumed fuel particles `thathit contains. The carbon tube and the annular conduit 2 terminate in a common tail pipe 33, which extends through the refractory lining 'l and opens tangentially in its inner survface Yin3the same `direction as the holes in the tuyeresj.` The tail pipe 33% passes combustion gases from the expansionchamber mixed with air from the air jacket, said air providing the necessary oxygen` for burning the unconsumed particles which are spontaneously ignited at the point at ywhich they enter the intensely hot combustion chamber.

The mantel `Ii slopes downward toward its outer periphery so as to cause such particles which may lodge on said mantel and are swept about by `the whirling gases, to gravitate outwardly and be Acaught in the funnel shaped depressions and drawn through the injector.

'Ih'e injectorsextend longitudinally through the refractoryhlining for the major portion of their length to present as great a surface as possible in heat exchangingcontact with the refractory material for cooling the latter, and the tail pipes of alternate injectors `extend to a lower level than the tail pipes ofthe remaining injectors, so that they open into the combustion chamber in separate intermediate zones at different levels, whereby they more or less uniformly distribute their cooling function throughout the mass of the refractory lining between the zones of the lower and upper tuyres.r All of the air entering the combustion chamber through the tuyres, injectors, and fuel pipe passes through the heated refractory lining and is preheated.

The down drift in the peripheral region of the expansion chamber atmosphere is inherently more feeble than the forces which tend to lift the central column of clarified combustion gases toward Vthe crown sheet of the boiler. Therefore, it is not felt in the upper regions of the expansion chamber, so that above the down drift the column of clarified combustion gases is free to expand outwardly as well as upwardly so that it extends to the shell b3 and thus becomes uniformly distributed throughout the entire area of the crown sheet and through all the tubes of the boiler, while the combustion gases within the eX- pansion chamber will have become centrifugally purged of all unconsumed particles by the time they reach the height at which they are unaffected by the down drift.

It will be understood that all of the air-admitting instrumentalities which pass through the refractory lining 'l are directly supported by the casing Ei and in turn lend support to said lining.

In a furnace constructed according to the teachingsY of the invention as herein disclosed, combustion is so complete that when the furnace is in normal operation, no smoke can be detected at the mouth of the stack. Neither is it necessary to remove any ashes over long periods of operation, since the noncombustible residue has the form o-f a light fly ash which is discharged from the stack suspended in the effluent gases. With certain types of fuel, a fused clinker may form in the bottom of the combustion chamber, and a clinker door 34 is provided at the base of the furnace, closing an opening to the combustion lchamber through which the clinker may from time to time be withdrawn. In general, however, this door is useful to admit air for quick cooling of the furnace when this becomes necessary, for making repairs, etc.

While I have in the above disclosure described what I believe to be a preferred vand practical embodiment of the invention, it will be understood by those skilled in the art that the specific details of the construction and arrangement of parts, as shown, are by way of example and not to be construed as limiting the scope of the inventi-on.

What I claim as my invention is:

1. In furnace construction, -means defining coaxial combustion and expansion chambers, the expansion chamber being above said combustion chamber and of larger diameter and capacity than said combustion chamber, said chambers communicating by way of a constricted central mouth which defines an upwardly facing annular mantel constituting the bottom of said expansion chamber, means for admitting comminuted fuel asi-asco to saidI combustion chamber; means for admitting air at the periphery offsaid cor'nbustionl chamber tangentially, producing a whirling atmosphere in said combustion chamber which persists in the column of combustion prcduc'rtsA that discharges through said mouth andexpandsinsafid expane sion chamber, whereby unccnsumed fuelparticlesr are centrifugally thrown to a peripheralzone of said expansionchamber above said mantel, passage means opening in saidl mantelleading to said `combustion chamber, and means for-withdrawing said centrifuga-ily displaced unconsur'nedt particles from said peripheralv zone andreturning them to said combustion chamber through said passages. i

2. In furnace construction, means defining coaxialV combustionand expansion chambers, the expansion chamber being" above saidv combustion chamber and of larger diameter and capacity than said combustion chamberjsaid chambers communicating by way efal constrictedcentral mouth which defines an upwardlyfacihg annular' mantelrconstituting the bottomsof saidfex'pan'sion chamber, means for admitting commi-muted f-uel to said Vcombustion cham-ber, meansfor admitting air at the periphery of sai-d combustionchamber tangentially,` producing a whirling atmospherein said combustion chamberl wh-i-ch-persists'in the column of combustion products that discharges` through said mouthv andeXpa-nds insa-id expansion chamber, whereby unconsumed fuely particles are cent ifugally thrown to a peripheral zone. of said expansion chamber above said-mantel, and injector means including` passages opening in said mantel and leading to said'combustion chamber for withdrawing said'centrif-ugally displaced unconsumed particles from said-peripheral zone and returning them to said-combustionchamber through said passages.

3. In furnacey construction, means` defining coaxial combustion and` expansion chambers, the expansion chamber being above saidcombustion chamber and of larger 'dia-meter*and*v capacity than said combustion chamber, said chambers directly communicating by' wayof acentral'constricted. mouth which deiines ari upwardly tacingy annular mantel constituting the bottom ot said expansion chamber,` a transverse sheetffo'rming theend of saidrexpansion chamberoppcste said mouth, having substantially-throughout its` entirety a plurality'oi substantially uniformly distributedopenings through which the-combustion gases. from saidv expansion' chamber discharge, mean-s for admitting comminuted fuei to said combustion chamber', means fork admitting air atrthe. periphery of saidl combustion chamber tangentially, producing a whirling# atmospherein said combustion chamber which persists.-v inthe colmnn of combustion productsv that; discharges through'said mouth: and expands in said sion chamber, whereby unconsumed'lfuel' partircies are centrifugally thrown to a peripheral@ zon-e of said expansion chamber aboveY vsaid mantel', and injectors' incl-udingpassages open-ing inffsaidf mantel leading to said combustion cham-beryfor withdrawing saidv centrifugal'ly displaced unconsui-ned particles -from-saidyperipheralzone. and returning them to said combustionchamher; =1

4. In furnace construction; a I'ceiniousticm chamber unit comprising a cylindrical-metal casing having asurrounding. laanjacket and' means' for suppl-ying air under pressure-:to said jacket,` an expansion chairiber uniti-comprzising ashell coaxial' with` said 'cohilirustionfchamhcr unit and resting thereupon havinga transverse 8 sheet at some distance from the lowerl end ofthe shell, the space within said she-ll' below/SaidI sheet constituting an expansion chamber, said sheet being provided substantially throughout its entirety with a plurality of substantiallyl uniformly distributed openings'for the discharge` ofcombustionv gases saidl casingI having aY refractory lining lwith vupwardly convergent sidesdefining acornbustion chamber having ay constricted mouthand forming an annular mantel surrounding said mouth constituting the bottom ofvsaid expansion chamber, the latter being of greater capacity than said combustion chamber,l a fuel pipe for feeding pulverized fuel to said' combustion chamber,- a circumferential series' of tuyres from said jacket extending through said refractorylining, opening tangentiallyV into said combustion chamber for producing a whirlingatmosphere therein which persists in the5- column of combustion products that discharges through said mouth toward said sheet and expands in said expansion chamber, wherebyunconsurned fuel particles are thrown to a peripheral zone of said expansion chamber above'said mantel, and a circumferential series of injectors, each includingV an air tube from said jacket opening into said combustion chamber, and a carbon tube having its upper end opening in said mantel', eX- tendilng into saidifaii tube axially thereof and terminating therewithin, whereby the How of air under pressure from said jacket past said carbon tubewithdraws said centrifugally displaced" unconsumed l particles from 'said peripheral Zone, returning them to said combustion chamber.

5. In furnace construction, a combustion chamber unit-adapted to be-installed beneath an expansion chamber of greater diameter and capacity than the 'combustionchamber and having-a` discharge at the end remote from said unit, said unit comprising a cylindricalcasingy having a" ja-cketedf space thereabout extending substantially Ythe height of the casing and supplied by airIunder pressure, a refractoryy lining Within said' casing including bottom and sidewalls, the latter converging inan upwardl direc-tion vderining a constricted mouth anda mantelsurrounding the mouth, saidl lining defining a combustion chamber, a circumferential series lof tuyres' entering said cox-nbustion` chamber vthrough said lining near the bottom, a circumferentialseries of upwardly andi-nwardly directed tuyies extending through said liningfenteringsaidcombustionchamber adjacent said mouth, the tu-yresof both-series opening tangentiallly in the same direction; a circumferential' series of injectors extending through said lining entering said combustion `cl'lamber-in a zone between said series of tuyres,` said injectors each including a carbon tubeV having its' upper endopening in-said mantel, and anair tube intol which the lower end of said carbon tube extends and opens, whereby the flow of` airY through said airl tube creates downward flow through said carbon tube, said tuyresl of both series andthe ailr tubes of said injectors being supported by said casing and communicating with said jacket.

6. Furnaceconstruction as claimedl in claim 5, including a fuel-pipe for feeding pulverized fuel to saidl combustion :chamber anda connection establishing communication betweensaid jacket and said fuel pipe. y

` 7. Furnace construction as claimed in claim 6, saidmantel sloping downwardly toward its outer periphery, and? the carbon tubes of said injectors opening into'said mantel 'near its outerperiphery.

'door opening lintermediate its height through said casing and refractory lining, a door hinged to said casing on the approach side of said opening with reference to the direction of said whirling atmosphere, said door closing against said casing, an inclined baiiie carried by said door in spaced relation thereto extending from the outer face of said lining on the approach side of said opening to the inner face of said lining on the opposite side of said opening, and a fuel pipe entering said combustion chamber adjacent the 10 approach side of said door opening having its inner end inclined toward said baille, for admitting fuel in a vehicle of air under pressure whereby the air cools said baie.

GEORGE T. LESTER, SR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,112,463 Meikle Oct. 6, 1914 1,657,698 Schutz Jan. 31, 1928 1,817,150 Hvoslef Aug. 4, 1931 1,918,397 Jezler July 18, 1933 1,943,949 Coghlan et al Jan. 16, 1934 1,967,883 Hofmann July 24, 1934 1,969,371 Hawley Aug. 7, 1934 2,424,765 McCollum July 29, 1947 

